Thermostat



pr 25, 1933- A. J. KERCHER 905,233

THERMOSTAT mun-a1 Filed July 29, 193

FIE; E

' nvmvrox Arf/zurJ A e/rfier AT TOR 45 tially wide temperature Patented Apr. 25, 1933 UNITED STATES PATENT err-ice ARTHUR J. KERCHER, F Jammy", CALIFORNIA rnnnmosrnr Application filed July 29, 1930, Serial No. 471,508. Renewed August 15, 1982.

This invention relates generally to thermostats for effecting a control in accordance with temperature changes of a given medium. It has particular application to devices of this character for controlling one or more electrical circuits, in accordance with the temperature of water, air or other medium. In thermostats of the above character it has been common to utilize a suitable temperature responsive element, as for examplc a bimetallic strip which will flex in accordance with tern erature changes, connected to a movable e ctrical contact in such a manner as to move the contact to either closed or open position with respect to a cooperating stationary contact. ,One of the chier defects of rior devices of this character has been a lac I of positive action to the movement of the electrical contact, which necessarily. results in arcing between the cont-acts'and in improper control of the associated'electrical circuit. This lack of positive action general- 1y manifests itself by a chattering of the contacts, and is most noticeable when the temperature change which should efl'ect operation of the contacts are relatively small. Attempts to secure more positive action by the use of tog le means have been only artially success 11!, and have generally en at the sacrifice of sensitivity.

It is a general object of the present invention to devise a thermostat'which will be characterized by the positive action of its contacts and which will also be.'relatively 35 sensitive in its action. As will be presently explained this object is attained ent invention by the use of a plurality of temperature responsive elements which are grrgnged to act additively thru a toggle r1 ge.

It is a further object of the invention to devise athermostat of relatively simple and rugged construction and which can be readily adjusted to efl'ect control over a substan'-' range.

in the pres- Further objects of the invention will appear from the following description in which the preferred embodiments of the invention have been set forth in detail. It is to be understood that the ap ended claims are to be accorded a ran e o equivalents consistent with the state of the prior art.

ferring to the drawing:

Figure 1 is a plan view illustrating athermostat ccnstructed in accordance with the or; present invention.

Fi 2 is a cross sectional view taken along the line a e of Fig. l

Fig. 3 is across sectional view taken along the line 3-3 of Fig. 1. I

Fig. is a detail in plan illustratin a modification of the thermostat shown in ig. 1.

Fig. 5 is a cross sectional detail taken along the line 5- 5 of Fig. 4:.

Referring first to that form ofthe invention shown in Figs. 1 to 3 inclusive, the device consists of a suitable mounting 10, which can conveniently be in the form of a. relatively rigid metal bar or stri As the device in this instance is adapte for the control of 76 one or more electrical circuits, I have shown a pair'of cooperating contacts 11 and 12. Stationarycontact 11 is carried by suitable means such as an upstanding member 13. Movable contact 12 is carried by one end of a lever arm 14, which in turn is connected to. temperature res onsive elements 16 and 17 to be presently escribed.

For limiting movement of contact 12 to open position and adjustable stop in the form 90 o a set screw 18 is provided, t is set screw bein carried b an upstanding member 19. For xing mem rs 13 and 19 to mounting 10, they are each shown provided with en posed laterally bent portions '21 and 22, wl ii ch are retained out of direct electrical contact with each other by means of insulatin disc 23. A screw 24 extends 'thru an o nmgin one end of mounting 10, thru one or opening in portion 22, and is threaded into mem-" her 21. An insulating washer 26 prevents direct electrical connection between portion 22 and mounting 10, while another insulating washer 27 prevents direct electrical connection between screw 24'and the mounting. terminal connector 28 facilitates the making of electrical connection with stationary contact 11, and another terminal connector 29 is provided for making electrical connection with movable contact 12. 4

Temperature responsive elements 16 and 17 are preferably in the form of bimetallic strips which tend to flex in response to temperature changes. Bimetallic strips of this character are well known in the art and are formed of two connected layers of metals having different temperature coefiicients of ex ansion. In orderto make the completed t ermostatas com act as possible, these strips are preferabl ormed spirally as shown. For connecting t ese stri s to the mounting I have shown a pair 0 superposed plates 31 and 32 which are pivotally connected .to mounting 10 by means of pivot pin 33. Pin 33 is normally retained in place by means of a 1eaf.spring 34 which engages the under side of mounting 10 and an abutment pin 36 inserted thru pin 33. An upturned flange 37 on plate 31 tends to add rigidit to the mounting for strips 16 and 17. he inner ends of strips 16 and 17 are fixed within slots provided in studs 38 and 39, and these studs are in turn mounted at spaced points upon plates 31 and 32.

The outer end portions and 41 of strips 16 and 17 are arranged so as to be in spaced proximity. 'The bimetallic layers of these elements are alsopreferably arranged so that each strip tends to uncoil in response to an increase m tem rature, and since the elements are coile in opposite directions, end portions 40 and 41 move in opposite directions responsive to like changes in temperature.

Interposed between the end portions 40 and 41 there is a toggle bridge 42, which in turn is connected to lever arm 14. The construction of this toggle bridge 42 can be made clear b reference to Fig. 3. The adjacent end of ever arm 14 is rovided with a portion 43 of enlarged wi th. This portion is provided with alined a rtures 44. Strips 48 and 49 of suitable insulating material, such as mica, are arranged upon 0 posite sides of portion 43. The strips can e held in proper position by means of rivets 50.

Studs 51 project thru insulating stri s 48v and 49 are alined with apertures 44, an each stud is provided with a projecting pivot point 52. The two pivot points 52 upon one side of the bridge engage indentations 53 in the adjacent en portion 40 of element 16, while the ivot point 52 upon the other side of the bri ge engages a cove 54 formed in the end portion 41 of ement 17 When the tog- A them in proper assemb gle bridge 42 is 'tioned between end portions 40 and 41 ese end portions are sprung apart to a substantial de so that pivot pms 52 are always urged inwardly to retain ed relationship.

In combination with the elements described above I also utilize means for adjusting the device for efiecting a control at any point over a substantial range of tem ratures. In

this instance this is accomplis ed by means for adjusting the angular position of plates 31 and 32 with respect to mounting 10. Thus plate 32 is shown provided with a projecting portion 57. A hand controlled lever 58 is pivotally connected to mounting 10 by means of threaded stud 59. Stud 59 is rovided with an excentric portion 61, which ts within a slot 62 provi ed in portion 57 There fore by chan ing the angular setting of lever 58, the an ar position of plates 31 and 32 can be ad usted between certain limits. It

should be noted howeverthat a change in the angular position of plates 31 and 32 with respect to mounting 10, is about the center of pivot pin 33, which intersectsthe line of centers between pivot pins 52 as viewed in Fig. 1.

In utilizing my device electrical connections to contacts 11 and 12 are made by connecting the circuit wires to binding posts 28 and 29. Binding post 29 is shown connected to lever 14, and thus to contact 12, by means of flexible lead 63. I

When the device is in operation toggle bridge 42 is subjected to turning torque to rotate the same in one or the other direction depending upon the temperature of strips 16 and 17 and upon setting of lever 58. The

turning torque is of course efl'ected by virtue of the tendency of end portions 40 and 41 to move in opposite directions in response to like changes of temperature in strips 16 and 17 The toggle efiect which makes positive movement of the contact 12, is roduced by virtue of the normal sprung con ition of the strips 16 and 17 whereby end portions 40 and 41 are always normally biased together upon the pivot pins 52. Of course for a given setting of lever 58, a certain temperature variation is required to effect movement of contact 12 from open to closed position or vice versa. Assuming now for a given adjustment of the device, the temperature of elements 16 and 17 is midway between such upper and lower limits, contact 12 will remain in either open or closed condition. Furthermore for such condition the toggle bridge will move thru a dead center position when the contacts are opened or closed. Therefore as the temperature varies between such limits, contact 12 is caused to move rapidly from either closed to open position, and the rapidity of movement is caused by upsetting the toggle formed by bridge 42. It is evident that if for one setting of lever 58 thecontacts will close at a given temperature, re-

I mounting and to the toggle bridge, will hav tacts Thus by varying 7 5 I have incorporated means in Fig. l, when lever the effect of requiring a different temperature of the strips 16 and 17 to close the conthe setting of lever 58 the contacts can be caused to close for any desired temperatureove'r a substantial temperature range.

As explained above-the positive movement of the contact is caused in art by the toggle action of bridge 42. It is a so caused in part by the fact that movements of the end portions 40 and 41 act additively upon the toggle bridge. This additive action renders the device sensitive, and also enables the use of relatively rugged bimetallic strips which are capable of exerting a relatively igh turning torque.

In the modification shown in Figs. 4 and for mechanically retaining the contacts in open position when the control lever is moved to a limiting position. Thus in this case the adjusting lever 66 is secured to threaded stud 59. graduated plate 67 is secured to mounting 10, whereby the settin, of lever 66 can be visually determined. ounted upon arms 14 and extending beyond pivot pin 52, there is an arm or tongue 68. The head 69 on stud 59 carries a projectingpin 71, adapted to engage one side of tongue 68. As viewed 66 is moved to the right to its limiting osition, pin 71 engages tongue 68, and there y positively retains contacts 11 and 12 in open position. Thus the device is rendered inoperative to eifect closin of the contacts for any temperature variations,

until lever 6 6 is manually moved from its limiting position.

I claim:

1. In an electrical control thermostat, a stationary contact, a movable contact movable between open and closed positions with ture changes, and means respect to the stationary contact, a pair of 1- metallic strips, a mounting to which an end of each strip is fixed, pivot pins serving as a connection between the free ends of the strips, said strips bein normally tensioned to urge the free ends 0 said strips together, a member connecting said pivot pins with the movable contact, said strips being arranged to flex oppositely responsive to like temperafor adjustably rockingsaid mounting about an axis intersecting the center line of said pivot pins, whereb both of said bimetallic strips and the mova is contact carrying member can be conditioned to effect closure of the contacts at a difierent temperature.

2. In an electrical control thermostat, a stationary contact, a movablecontact movable between open and closed positions with respect to the stationary contact, a pair of bimetallic strips, a mounting to which an bridge and end of each strip 'is fixed," the free ends of said strips being in opposed spaced proxim-- nection with the same, said strips being nornally tensioned to press toward the points 0 ten s to rotate in either direction past dead center position, I

said bein arranged to flex oppositely responsive to li e temperature changes, means for adjustably rocking-said mounting about an axis passing through the center of said bridge member, whereby both of said bimetallic strips and said movable contacts can be con ditioned to effect closure of said contacts at any desired temperature within the range of adjustability, der the control of a single and actuated lever, and a restraining member made operative upon movement of said lever to one of its extreme positions for precluding closure of said contacts in response to temperature chan es. 1

3. n an electrical contacting device, a stationary contact, acooperating contact n1ovable between open and closed positions relative to the stationary contact, a pair of oppositely spiraled resilient strips, mounting means to which an end of each strip is fixed, a toggle bridge pivotally connected to the free end of said strips, said strips being normally tensioned to urge the free ends thereof toether, a lever arm connecting said toggle jridge to said movable contacts, and means ivotal connection whereby the bridge a. member connecting said movable contact, said strips said adjustinglmeans being unan inner endof each strip is fixed, a toggle bridge pivotally connected to the free ends of said strips, said strips being normally tensioned to urge the free ends thereof together, a lever arm connecting said toggle brid e to said movable contact, and means for shi ing the position of the mounting means for the inner ends of said strips with respect to said stationary contact, sai strips being arranged to flex oppositely respons ve to like changes in temperature.

5. In an electrical contacting device, a toggle bridge, a lever arm having one end thereof mounted upon said toggle bridge, a contact carried by the free end of said arm, a station ary contact adapted to cooperate with said movable contact, a support to which said stationary contact is secured, a structure pivotall secured to said support adjacent said togg e bridge, means forming a pivotal con-f nection between said structure and one side of saidtoggle bridge, and resilient means forming a pivotal connection between the other side of said toggle bridge and said structure, said last means serving to apply resilient force to said toggle bridge, the components of which cause rapid opening and closing of said contacts thru rotation of the toggle bridge.

In testimony whereof, I have hereunto set my hand.

ARTHUR J. KERCHER. 

